This invention relates to porous microcomposites comprising perfluorinated ion-exchange polymers (PFIEP) containing pendant sulfonic acid groups and/or pendant carboxylic acid groups entrapped within and highly dispersed throughout a metal oxide network, prepared using a sol-gel process. Due to their high surface area and acid functionality these microcomposites possess wide utility as improved solid acid catalysts.
U.S. Pat. No. 5,252,654 discloses polymeric composites comprising an interpenetrating network of an organic polymer and an inorganic glassy polymer and a process for making such composites. The disclosed material is nonporous, and the use of perfluorinated ion-exchange polymers (PFIEP) containing pendant sulfonic acid groups or pendant carboxylic acid groups is not disclosed.
K. A. Mauritz et al., Polym. Mater. Sci. Eng. 58, 1079-1082(1988), in an article titled xe2x80x9cNafion-based Microcomposites: Silicon Oxide-filled Membranesxe2x80x9d, discuss the formation of micro composite membranes by the growth of silicon oxide microclusters or continuous silicon oxide interpenetrating networks in pre-swollen xe2x80x9cNAFION(copyright)xe2x80x9d sulfonic acid films. xe2x80x9cNAFION(copyright)xe2x80x9d is a registered trademark of E. I. du Pont de Nemours and Company.
U.S. Pat. No. 5,094,995 discloses catalysts comprising perfluorinated ion-exchange polymers (PFIEP) containing pendant sulfonic acid groups supported on an inert carrier having a hydrophobic surface comprising calcined shot coke.
U.S. Pat. No. 4,038,213 discloses the preparation of catalysts comprising perfluorinated ion-exchange polymers (PFIEP) containing pendant sulfonic acid groups on a variety of supports.
The catalytic utility of perfluorinated ion-exchange polymers (PFIEP) containing pendant sulfonic acid groups, supported and unsupported has been broadly reviewed: G. A. Olah et al., Synthesis, 513-531(1986) and F. J. Waller, Catal. Rev.-Sci. Eng., 1-12(1986).
This invention provides a porous microcomposite comprising perfluorinated ion-exchange polymer containing pendant sulfonic and/or carboxylic acid groups entrapped within and highly dispersed throughout a network of metal oxide, wherein the weight percentage of perfluorinated ion-exchange polymer in the microcomposite is from about 0.1 to 90 percent, preferably from about 5 to about 80 percent, and wherein the size of the pores in the microcomposite is about 0.5 nm to about 75 nm.
In a separate embodiment, the microcomposite can simultaneously contain larger pores ranging from about 75 nm to about 1000 nm, wherein these larger pores are formed by introducing acid-extractable filler particles during the formation process.
This invention further provides the process of preparation of a porous microcomposite which comprises perfluorinated ion-exchange polymer containing pendant sulfonic and/or carboxylic acid groups entrapped within and highly dispersed throughout a network of metal oxide, wherein the weight percentage of perfluorinated ion-exchange polymer in the microcomposite is from about 0.1 to 90 percent, and wherein the size of the pores in the microcomposite is about 0.5 nm to about 75 nm;
said process comprising the steps of:
a. mixing the perfluorinated ion-exchange polymer with one or more metal oxide precursors in a common solvent;
b. initiating gelation;
c. allowing sufficient time for gelation and aging of the mixture; and
d. removing the solvent.
In a further preferred embodiment the process further comprises at step (a), adding to the mixture an amount from about 1 to 80 weight percent of an acid extractable filler particle, after d;
e. acidifying the product of step d by the addition of acid; and
f. removing the excess acid from the microcomposite;
to yield a microcomposite further containing pores in the range of about 75 nm to about 1000 nm.
The present invention also provides an improved process for the nitration of an aromatic compound wherein the improvement comprises contacting said aromatic compound with a catalytic microcomposite of the present invention, described above.
The present invention further provides an improved process for the esterification of a carboxylic acid with an olefin wherein the improvement comprises contacting said carboxylic acid with a catalytic microcomposite of the present invention, described above.
The present invention also provides an improved process for the polymerization of tetrahydrofuran wherein the improvement comprises contacting said tetrahydrofuran with a catalytic microcomposite of the present invention, described above.
The present invention further provides an improved process for the alkylation of an aromatic compound with an olefin wherein the improvement comprises contacting said aromatic compound with a catalytic microcomposite of the present invention, described above.
The present invention provides an improved process for the acylation of an aromatic compound with an acyl halide wherein the improvement comprises contacting said aromatic compound with a catalytic microcomposite of the present invention, described above.
The present invention further provides an improved process for the dimerization of an alpha substituted styrene, wherein the improvement comprises contacting said alpha substituted styrene with a catalytic microcomposite of the present invention, described above.
The present invention further provides a process for regenerating a catalyst comprising a microcomposite of the present invention, as described above, comprising the steps of: mixing the microcomposite with an acid, and removing the excess acid.
The present invention also provides a process for the isomerization of an olefin comprising contacting said olefin at isomerization conditions with a catalytic amount of a porous microcomposite, said microcomposite comprising perfluorinated ion-exchange polymer containing pendant sulfonic and/or carboxylic acid groups entrapped within and highly dispersed throughout a network of metal oxide, wherein the weight percentage of perfluorinated ion-exchange polymer in the microcomposite is from about 0.1 to 90 percent, preferably from about 5 to about 80 percent, most preferably from about 5 to about 20 percent and wherein the size of the pores in the microcomposite is about 0.5 nm to about 75 nm.